/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.apache.coyote.http11.filters;

import java.io.IOException;

import org.apache.tomcat.util.buf.ByteChunk;

import org.apache.coyote.InputBuffer;
import org.apache.coyote.Request;
import org.apache.coyote.http11.InputFilter;

/**
 * Identity input filter.
 * 
 * @author Remy Maucherat
 */
public class IdentityInputFilter implements InputFilter {

	// -------------------------------------------------------------- Constants

	protected static final String ENCODING_NAME = "identity";
	protected static final ByteChunk ENCODING = new ByteChunk();

	// ----------------------------------------------------- Static Initializer

	static {
		ENCODING.setBytes(ENCODING_NAME.getBytes(), 0, ENCODING_NAME.length());
	}

	// ----------------------------------------------------- Instance Variables

	/**
	 * Content length.
	 */
	protected long contentLength = -1;

	/**
	 * Remaining bytes.
	 */
	protected long remaining = 0;

	/**
	 * Next buffer in the pipeline.
	 */
	protected InputBuffer buffer;

	/**
	 * Chunk used to read leftover bytes.
	 */
	protected ByteChunk endChunk = new ByteChunk();

	// ------------------------------------------------------------- Properties

	/**
	 * Get content length.
	 */
	public long getContentLength() {
		return contentLength;
	}

	/**
	 * Get remaining bytes.
	 */
	public long getRemaining() {
		return remaining;
	}

	// ---------------------------------------------------- InputBuffer Methods

	/**
	 * Read bytes.
	 * 
	 * @return If the filter does request length control, this value is
	 *         significant; it should be the number of bytes consumed from the
	 *         buffer, up until the end of the current request body, or the
	 *         buffer length, whichever is greater. If the filter does not do
	 *         request body length control, the returned value should be -1.
	 */
	public int doRead(ByteChunk chunk, Request req) throws IOException {

		int result = -1;

		if (contentLength >= 0) {
			if (remaining > 0) {
				int nRead = buffer.doRead(chunk, req);
				if (nRead > remaining) {
					// The chunk is longer than the number of bytes remaining
					// in the body; changing the chunk length to the number
					// of bytes remaining
					chunk.setBytes(chunk.getBytes(), chunk.getStart(),
							(int) remaining);
					result = (int) remaining;
				} else {
					result = nRead;
				}
				remaining = remaining - nRead;
			} else {
				// No more bytes left to be read : return -1 and clear the
				// buffer
				chunk.recycle();
				result = -1;
			}
		}

		return result;

	}

	// ---------------------------------------------------- InputFilter Methods

	/**
	 * Read the content length from the request.
	 */
	public void setRequest(Request request) {
		contentLength = request.getContentLengthLong();
		remaining = contentLength;
	}

	/**
	 * End the current request.
	 */
	public long end() throws IOException {

		// Consume extra bytes.
		while (remaining > 0) {
			int nread = buffer.doRead(endChunk, null);
			if (nread > 0) {
				remaining = remaining - nread;
			} else { // errors are handled higher up.
				remaining = 0;
			}
		}

		// If too many bytes were read, return the amount.
		return -remaining;

	}

	/**
	 * Amount of bytes still available in a buffer.
	 */
	public int available() {
		return 0;
	}

	/**
	 * Set the next buffer in the filter pipeline.
	 */
	public void setBuffer(InputBuffer buffer) {
		this.buffer = buffer;
	}

	/**
	 * Make the filter ready to process the next request.
	 */
	public void recycle() {
		contentLength = -1;
		remaining = 0;
		endChunk.recycle();
	}

	/**
	 * Return the name of the associated encoding; Here, the value is
	 * "identity".
	 */
	public ByteChunk getEncodingName() {
		return ENCODING;
	}

}
